[CI] Stale Github Actions runs now automatically cancelled

[Antoine Pitrou <an...@python.org>]

Hello,

Just an announcement that, since
https://github.com/apache/arrow/pull/9455 has been merged, stale CI jobs
on Github Actions should now be automatically cancelled.

By "stale jobs", we mean a job that concerns a changeset that has been
superseded by another changeset on the same PR (note this doesn't apply
to pushes to git master, since it is beneficial to know precisely which
changesets on the main branch failed or succeeded CI).

Since this leverages a dedicated third-party action, there should
ideally not be any problem, but don't hesitate to report any unexpected
or undesired behaviour.

Regards

Antoine.